The present invention relates to an epoxy-based curable composition or, more particularly, to a room temperature curable epoxy-based composition having improved curability and adhesivity as well as improved stability when stored in one package as ready-mixed.
As is well known, epoxy resins are excellent in mechanical strengths, adhesivity on to various substrate materials including metals, ceramics, masonry materials and the like and chemical stability against alkalis as well as in the very small shrinkage by curing so that they are widely used in a wide variety of application fields such as adhesive agents or as a binder resin combined with certain reinforcing materials such as glass fibers, powdery fillers and the like to give reinforced composite resinous materials to be used in various kinds of electric instruments or machinery.
One of the problems in the epoxy resins in the prior art is, however, that a curable epoxy resin composition is obtained only by blending two components, which are stored separately in two packages, directly before use or, in other words, the epoxy resins are of two-package type so that troublesome procedures of weighing, admixing and blending of the components are always indispensable in addition to the problem that a relatively long time is required for complete curing of the thus prepared resin compositions.
Accordingly, various attempts have been made recently to solve the above described problems in the prior art epoxy resins in the direction of obtaining a so-called one-package type epoxy resin composition which is storable as ready-mixed in one package. The one-package type epoxy resin compositions of the prior art utilize in principle a latent curing agent which exhibits curing activity only when it is heated in the composition as exemplified by complex compounds of boron and an amine, dicyandiamide, ketimine compounds, boron trifluorideamine complex compounds and the like. It is of course necessary that such an epoxy resin composition must be heated at an elevated temperature to be cured sufficiently rapidly taking a considerably long time of heating. In addition, most of the above named latent curing agents produce poisonous or corrosive gases with unpleasant odor by heating so that a sufficiently powerful ventilation unit is required in order to keep healthly working environments. Further, the corrosive decomposition products of the curing agents cause rusting of metals when the epoxy resin composition is applied on to the surface of a metal surface so that it is indispensable that the metal substrate must be treated in advance with a primer.